1. Field of the Invention
The present invention relates to an automatic document feeder that is a mechanism to automatically supply documents to an image reading unit and in particularly, improves productivity in reading both sides of documents.
2. Description of Related Art
In automatic conveying units that supply documents automatically to an image reading unit such as a scanner and the like, some of them supply both the front and back sides of documents to an image reading unit. In such an automatic document feeder that is capable of supplying both sides of a document, it is desirable that a collating order of a document placed on a paper supply tray before reading the document is the same as the collating order of the document discharged on a paper discharge tray after completing the image reading in either cases to read a document image on one side only or document images on both sides.
In the Japanese Patent Application Publication No. 2002-220149, a technology is proposed to place documents on a paper supply tray with their front sides upward and supply them to an image reading unit first from a document put on the top in the case of reading both sides and after reading the front side, reverse the document for reading the back side and after reading the back side, reverse the document again by the reversing mechanism and discharge through the paper exit and thus, the document in the same collation order as that before supplying the documents with the front side downward is discharged onto a paper discharge tray.
However, in the conventional technology mentioned above, it is considered to discharge documents by collating them but the documents are discharged in the as-is state onto the discharging tray in the open state and alignment of discharged documents is not considered. As a result, it was necessitated for operator to align documents after completing the reading. Further, when documents are relatively small in size, the collation might become out of order on the paper discharge tray.
Accordingly, in an automatic document feeder capable of supplying both sides of documents to an image reading unit, it is demanded to discharge documents on the paper discharge tray in the same collation order and good aligned state as before the reading.